Mechanical writing instrument

ABSTRACT

A mechanical writing instrument having a substantially flat body shaped such that the writing instrument may be used as a bookmark or the like. At least two writing members are disposed within the body and are mounted for reciprocal movement therein. The writing members each include manual actuating fingers operable for moving the writing members between their respective retracted positions and writing positions and for maintaining the writing members in these positions.

United States Patent 1 Zepell MECHANICAL WRITING INSTRUNIENT Nathan A. Zepell, 1359 Santa ,Teresita Drive, Santa Barbara, Calif.

[22] Filed. May 1, 1974 [21] Appl. No: 465,752

Related US. Application Data [(13] Continuation of Ser, No. 322,770, Jan. 13, 1973,

{76] Inventor:

1 1 Oct. 14, 1975 FOREIGN PATENTS OR APPLICATIONS 382,737 10/1923 Germany 401/31 1,008,145 5/1957 Germany 1111 401/31 264.326 1/1950 Switzerland 401/30 51 255 11/1941 France 401/31 Primary Examiner-Lawrence Charles Attorney, Agent, or FirmAmster & Rothstein [57] ABSTRACT A mechanical writing instrument having a substantially flat body shaped such that the writing instrument may be used as a bookmark or the like. At least two writing members are disposed within the body and are mounted for reciprocal movement therein. The writing members each include manual actuating fingers operable for moving the writing members between their respective retracted positions and writing positions and for maintaining the writing members in these positions.

6 Claims, 17 Drawing Figures U.S. Patent Oct. 14, 1975 Sheet 1 0f3 3,912,401

F|G.2. FIG. I. I FIG. 3. F|G.4.

US. Patent 0a. 14, 1975 Sheet 2 of3 3,912,401

FIG. 7. FIGS. FIG. \O.

US. Patent Oct. 14, 1975 Sheet 3 0f 3 3,912,401

2 a fizz n E Z! FIG. \5. FIG. l6.

MECHANICAL WRITING INSTRUMENT This is a continuation of application Ser. No. 322,770, filed .lan. ll, I973 (now abandoned).

This invention relates generally to writing instru ments and, more particularly, to a mechanical writing instrument including a plurality of writing members.

Mechanical writing instruments, such as mechanical pens, pencils, or the like, are generally well known in the art and often include a plurality of writing members which may be selected by a user. However, the prior art writing instruments of this type have been less than successful in that they are generally bulky in configuration, difficult to operate and expensive to manufacture.

Accordingly, it is a broad object of the present inven' tion to provide a mechanical writing instrument which overcomes the difficulties experienced with writing in struments of the prior artv Specifically, it is an object of this invention to provide a mechanical writing instrument having a plurality of writing members which is slim or non-bulky in shape, is easy to manipulate or operate and may be manufactured relatively easily and inexpensively on a mass-production basis.

In accordance with an illustrative embodiment demonstrating objects and features of the present invention, there is provided a mechanical writing instrument having a plurality of writing points which comprises a body having opposed substantially flat faces and at least two channels disposed in a substantially common plane intermediate the flat faces. The two channels merge into a common point opening at one end of the body. At least two writing members, each having a writing point which is disposed in the channels in retracted position, are mounted for reciprocation in the channels in order to extend their respective writing points through the point opening into an extended writing position. Manual actuating means are operatively connected to each writing member and extend exterior to the body for manually moving the writing members in their channels toward and away from the point opening and into and out of the extended writing positions. The spacing between the opposed substantially flat faces of the body are established to provide the requisite structural walls for the channels yet minimize the dimension of the body at right angles to the common plane thereby providing a body for the writing instrument which is relatively flat in configuration.

The above brief description, as well as further objects, features and advantages of the present invention will be more fully understood by reference to the following detailed description ofa presently preferred but nonetheless illustrative embodiment in accordance with the present invention, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a front elevation view of a mechanical writing instrument according to the present invention;

FIG. 2 is a left side elevation view of the mechanical writing instrument of FIG. 1;

FIG. 3 is a right side elevation view of the mechanical writing instrument of FIG. 1;

FIG. 4 is a rear elevation view ofthe mechanical writing instrument of FIG. I;

FIG. 5 is a bottom plan view, slightly enlarged in scale, of the mechanical writing instrument of FIG. 1;

FIG. 6 is a top plan view, slightly enlarged in scale, of the mechanical writing instrument of FIG. 1;

FIG. 7 is a front elevation view. partly in section. of a ferrule and one piece of the body of the mechanical writing instrument;

FIG. 8 is a front elevation view of the other piece of the body of the mechanical writing instrument showing two writing members disposed within the body;

FIG. 9 is a sectional view, enlarged in scale, taken substantially along the line 9-9 of FIG. 8 and looking in the direction of the arrows, but showing both pieces or halves of the body;

FIG. 10 is a partial rear view ofthe mechanical writing instrument showing the insertion or removal of one of the writing members;

FIG. 11 is a partial sectional view, enlarged in scale, taken substantially along the line II-ll of FIG. I and looking in the direction of the arrows;

FIG. 12 is a top plan view, enlarged in scale, of the writing instrument of FIG. It) with the clip removed from the illustration for clarity;

FIG. 13 is an enlarged view of a portion of the mechanical writing instrument of FIG. 8 but illustrating one ofthe writing members in a position between its retracted position and extended writing position;

FIG. 14 is a right side elevation view of FIG. 13, but showing both pieces or halves of the body;

FIG. 15 is a left side elevation view, partly in section. of part of one of the writing members utilized in the mechanical writing instrument ofthe present invention with part of the cartridge broken away;

FIG. 16 is a front elevation view of the writing mem ber of FIG. 15; and;

FIG. 17 is a sectional view, enlarged in scale, taken substantially along the line l7l7 of FIG. 13 and look ing in the direction of the arrows, but showing both pieces or halves of the body.

Referring now to the drawings and, more particularly, to FIGS. 1-8 thereof, a mechanical writing instrument according to the present invention is generally designated I0 and includes a body, generally designated 12, in which is disposed writing members, generally designated 14, I6. A clip, generally designated 18, is mounted near the top 20 of body 12 and is provided such that mechanical writing instrument It) may be secured within a pocket or the like as is generally understood in the art.

Body 12 is of a two-piece construction and includes substantially identical and symmetrical body members 22, 24 which are adapted to be maintained in confronting relation with each other, for example, by a ferrule 26 located at the bottom of the body members and by clip 18 located at the top of the body members. Alternatively, or in addition thereto, body members 22, 24 may be maintained in opposed relation by cementing these two pieces or halves of body 12 together.

Body member 22 is relatively flat and tapered in configuration and includes a substantially flat face 28 having a width which generally decreases from the top to the bottom thereof (see FIG. I). Body member 22 is also formed with opposed side faces forming side walls, generally designated 30, which are generally perpen dicular to the plane formed by face 28. Referring to FIG. 7, body member 22 includes a substantially V- shaped portion 32 which extends inwardly from face 28 intermediate of side walls 30. Thus, V-shaped portion 32 and side walls 30 form guideways, generally desig nated 34a, 34b in body member 22 with the guideways open and separated from each other at the top of body member 22 and converging, as indicated at 34c. near the bottom of the body member. The guidcways ICtIlll nate at an opening 34d in body member 22. As will be explained hereinafter, guideways 34a. 34b of body member 22 are adapted to cooperate with corresponding and ymmetrical guidcways in body member 24 to define two cartridge channels which are adapted to re ccivc writing members I4. 16.

Body nicmbei 24 is substantially identical to and symmetrical with body member 22. Thus, body mem her 24 is relatively flat and tapered in configuration and includes a substantially llat face 28' of a width which generally decrea es from the top to the bottom of the body member and opposed side faces forming side mills. generally designated 30'. generally pcrpendicu' lar to the plane formed by face 28. Guideways. getter ally designated 3411'. 34/1 are formed by side walls 30 and a shapcd portion 32 of body member 24 such that the guidcviays are separated from each other and open at the top of the body member and converge, as indicated at 34: terminating at an opening 34:!" at the bottom or the body member,

Body member 22 and body member 24 are adapted to be held in confronting relation such that the corre sponding guidcways of these members define a first cartridge channel. generally designated 36. and a sec mid and substantially identical cartridge channel. generally designated 38, formed in body 12 (sec FIGS, 9 and [2 l which are adapted to receive respective writing members l4, l6. Cartridge channel 36, which is adapted to receive writing 14, and cartridge channel 38, which is adapted to receive writing member 16. arc generally identical and symmetrical in configuration and are disposed in a substantially common plane intermediate faces 28, 28 of body 12.

Each cartridge channel includes a top channel portion 36a or 38;: which is generally Ushaped in cross section and which defines a corresponding cartridgereceiving opening 40 or 42 at the top 20 of body 12 tsec FlG. 12!. Cartridge channels 36, 38 converge. near the bottom of body 12, to define a common channel portion. generally designated 37, which common channel portion corresponds to the common or con verged portions 34c. 34c of the guideways. The comnion channel portion 37 terminates at a point opening 44 located at the end or bottom of body 12(see FIG, 5] with this point opening being formed by the corrc sponding openings 34d, 34d of the guidcways, lntermediate the top channel portions 360, 38a and the common channel portion 37. each cartridge channel includes respective intermediate channel portions 36b, 3% isec FIG 9), generally circular cross section, which are adapted to receive the cylindrical ink cartridges or refills" of writing members l4, l6.

Referring now to FIGS. l4, l0 and H, clip 18 is adapted to be removably mounted at the top 20 of body 12 and includes a top portion 18a and sides 18b, [81 depending downwardly therefrom. Clip 18 is sized such that body l2 may be inserted between sides 18b, 18c with the clip frictionally engaging body 12. In order to further secure clip IS to body 12, body member 24 may be formed with a notch 24a (sec FIGS. l0 and II) which is adapted to cooperate with an inwardly extend ing projection Illa located on side 18c. with the projection adapted to fit into the notch as indicated in FIG. ll. With clip ll'l mounted at the top 20 of body memher 12. the top lBii of clip i8 substantially blocks or covers the CHHfldgC'l'LLL ing openings 40, 42 disposed at the top of body l2 (compare FIGS, 6 and 12]. As will be explained hereinafter. clip 18 thereby helps to maintain writing members l4, [6 within body 12. It is to be noted, however, that clip 18 may be removed from the top of body 12 in order to provide access to cartridgc-rccciving openings 40,42, for example, by rising a finger l'orcc sufficient to overcome the frictional force between clip 18 and body 12.

Extending downwardly from side 18b. clip IS in eludes arms 18c, l8f'[scc NC. I) which arc bent away from side 18b (see FIG. 2) and which converge at clip end 18g A clip projection [8h extends downwardly from clip 18gand makes contact with face 28 of body 12. As is generally understood, arms 181 ll'ifand clip projection 18!: ofclip I8 function to secure mechanical writing instrument [0 within a pocket of the like or the user, for example. by securing writing instrument to a piece of material which is inserted between clip protection 181i and face 28 of body 12.

Mechanical writing instrument It] includes writing members l4, 16 which. by way of example, may be of a type generally referred to as *ballpoint" pens or the like. As indicated in FIGS. 8 and I347, writing mcmhers l4, 16 are substantially identical to each other with each writing member including respective pcn cartridgcs 46, 46' terminating in "ball" or writing points 48, 48'. Pen cartridge 46 and writing point 4811f writing member 14 and pen cartridge 46' and writing point 48' of writing member 16 are similar to conventional ballpoint pen rel'ills" with each cartridge being filled with ink 50, 50. Advantagcously, ink 50 in cartridge 46 is different in color than ink 50 in cartridge 46'.

As will be explained in more detail hereinafter, rcsil icnt clips. generally designated 52, 52' are located, respectively, at the top of writing members [4, l6 and are provided for manually moving the writing members toward and away from point opening 44. Specifically, the resilient clips are provided to move the writing members between their respective retracted positions and extended or writing positions.

Resilient clip 52, which is substantially identical to resilient clip 52', is generally U-shapcd in configuration and includes a downwardly extending projection 52a which is adapted to be inserted into the top of cartridge 46 in order to secure the resilient clip to the cartridge. Writing member 14 may be factory assembled and sold with resilient clip 52 and cartridge 46 as a unit (for example. as a single refill for the writing instrument] or. in the alternative, writing member 14 may be constructed such that the resilient clip is removable from the cartridge enabling the user to disgard empty cartridges while retaining the clip which may be inserted into conventional "refills" which may be purchased separately,

An air slot 52b extends between projection 52a and one leg 52c ofclip S2 in order to enable air to enter cartridge 46 in order to provide a proper How of ink 50 out of writing point 48. Leg 52! is adapted to abut cartridge 46 at the top thereof as indicated in FIG. 15. The other leg. 52d, of resilient clip 52 is adapted to fit into openings in body 12. Specifically, and referring to FIGS. I346. leg 52d is formed to include ribs or flanges 52c disposed on each side ofa projection 52fwhich extends upwardly from the ribs or flanges (see FlG. l6) Projcction SZfincludes a linger-receiving clement 52g having appropriate ridges 52h along the periphery thereof.

Located at the end of leg 52d and extending outwardly from each side of fingerreceiving element 52g are locking elements 52i which are adapted to fit into corresponding lock-receiving notches formed in body 12 in order to maintain the mechanical writing instrument its retracted position or in its extended writing position, as will be explained in more detail hereinafter. The end of leg 52d opposite ridges 52h of fingerreceiving element 52g is chamferred, as indicated at 52j, thereby enabling leg 52d to be flexed toward cartridge 46 (see FIG. 13) as will be explained hereinafter.

As with body members 22 and 24, writing member 16 is substantially identical to writing member 14. Thus, writing member 16 includes a cartridge 46' which terminates, at one end thereof, in a writing point 48'. Disposed at the top of cartridge 48 is a generally U- shaped resilient clip 52', formed with legs 52c and 52d. Further description of writing member 16 is deemed unnecessary, it being understood that the refcrence numerals having a prime designation correspond and are substantially identical to the parts of writing member 14 which have heretofore been de scribed.

Referring to FIGS. 13 and 14, side walls 30 of body member 22 and side walls 30' of body member 24 are formed such that when body member 22 is held in confronting relation with body member 24, the respective side walls define cartridge-guiding tracks, generally designated 54. disposed on each side of body 12. Tracks 54 extend along each side of body 12, substantially from the middle of the body to the top 20 of the body; that is, each track extends along the side of body 12 a distance corresponding to top cartridge channel portions 360 and 380. Each track is shaped to include a lock-receiving notch 56a, disposed intermediate the length of track 54, and a lock-receiving notch 56b, dis posed at the lower end of track 54. Lock-receiving notches 56a and 56b are somewhat wider in width than the rest of track 54 (see FIG. 14) and are adapted to receive corresponding lock elements 521' or 521" in order to maintain the writing members in retracted positions on in extended writing positions. Further, the width of tracks 54 are sized such that projection 52for projection 52)" of the resilient clips is adapted to fit into track 54 thereby enabling the respective writing members to be moved, in a reciprocating manner, from the retracted to writing positions.

In order to provide a more complete understanding of the present invention, a typical assembly and opera tional sequence of mechanical writing instrument will now be described.

Mechanical writing instrument 10 is formed substantially from body members 22, 24, writing members X4, 16 and clip 18. Production costs are held low since there are relatively few parts. Further, since the parts are not especially complex in shape, costs of molds, etc. are also held low.

Body 12 is assembled such that body member 22 is held in opposed or confronting relation with body member 24, for example, by permanently fastening the body members together, as by utilizing cement or heatbonding or the like. With body members 22 and 24 so assembled. the various guideways formed in the body members cooperate to form cartridge channel 36 and cartridge channel 38 with the cartridge channels disposed in a substantially common plane intermediate the flat faces 28 and 28' of the body members. Cartridge channel 36 and cartridge channel 38 are separate from each other and open at the top 20 of body 12 to include cartridge-receiving openings 40, 42. However, the cartridge channels merge into a common point opening 44 formed at the bottom of body [2.

As indicated in the various figures, body 12 is formed to be generally flat in configuration, for example, the spacing between the opposed substantially flat faces 28, 28' is established to provide the requisite structural walls 30, 30' for the cartridge channels but are so sized as to minimize the dimension of body 12 at right angles to the plane of the faces. Thus, body 12 is relatively flat in configuration and, as a result thereof. the mcchani cal writing instrument is easily adapted to be used not only as a writing instrument but also as a bookmark or the like. Body 12 is also tapered in configuration with side walls 30, 30 converging toward point opening 44.

After body 12 has been assembled, writing member 14 and writing member 16 are inserted into their respective cartridge channels, that is, writing member 14 is inserted into cartridge channel 36 through cartridgereceiving opening 40 and writing member 16 is inserted into cartridge channel 38 through cartridge-receiving opening 42. The writing members are inserted into the cartridge channels such that legs 52d, 52d of resilient clips 52, 52 cooperate with the tracks 54 formed along each side of body 12.

Specifically, writing member 14 is inserted into cartridge channel 36 such that projection 52f fits into track 54 and locking elements 521' fit into lock receiving notch 56a. This may be accomplished by exerting a slight finger pressure against finger-receiving element 52g as the writing instrument is inserted into cartridge channel 36 (of course, the resilient clip must be oriented such that projection 52d is in the track) and allowing the leg 52d of the resilient clip to spring back" into place once the locking elements 521' have reached lock-receiving notch 560. Note that resilient clip 52 is designed such that leg 52d is biased against the side walls 30, 30' of body 12 that is, the ribs or flanges 52e of the clip are biased against the side walls. With locking elements 521' in lock-receiving notch 56a, writing instrument 14 is maintained in a "retracted" position, with one end of the writing member, i.e., the top of clip 52, being disposed near the top 20 of body l2 and the other end of the writing member, i.e., the bottom or tip of writing point 48, being disposed near the converged or common channel portion 37 (but still maintained in intermediate channel portion 36b).

In a similar manner, writing member 16 is inserted into cartridge channel 38 with leg 52d of resilient clip 52 cooperating with track 54 and. more particularly, with projection 52 and ribs or flanges S2e' guiding the writing member in the track. Writing member 16 is inserted in the cartridge channel to a point where locking projection 52:" springs into notch 56a (see FIGS. 8, l3 and 14).

After both writing members have been inserted into their respective writing channels, clip 18 is snapped on to the top of body 12 with projection [8d of the clip inserted into notch 24a of body member 24. With clip 18 in place, it is readily apparent that the top [8a of the clip closes off the cartridge-receiving openings 40, 42 and, therefore, helps to maintain the writing members l4, 16 within body 12.

In operation, both writing members 14, 16 are disposed within body 12 such that the writing members are mounted for reciprocal movement from their retracted positions to their extended writing positions. Note that although writing members l4, l6 lie in a common plane within body 12, the longitudinal axes of the writing members are not parallel, that is, the longi tudinal axes of the writing members converge toward the point opening. When a user desires to write with writing member [4 or writing member 16 (which may depend. for example, on the particular color ink desired), the user moves the chosen writing member from its retracted position to its extended writing position such that the writing point extends out of the point opening of body l2. For example, if writing member 14 is chosen, the user applies finger pressure to finger receiving element 52g, pressing leg 52a inwardly relative to leg 52c and the rest of the writing member, thereby causing locking elements 521' to clear lockreceiving notch 56a. Maintaining this pressure, the user moves the finger-receiving element toward notch 56b causing writing member 14 to move towards point opening 44. Note, however, that projection 52fis still within track 54 (see FlG. l3) and the resilient clip still guides the writing member in track 54 as the writing member is moved in cartridge channel 36.

Continued motion of the finger-receiving element 52g toward notch 56b causes writing member 14 to reach its extended writing position (see FIG 8) in which the locking elements 521' have reached lockreceiving notch 56b, corresponding to writing point 48 being extended through point opening 44. Further movement of writing member 14 toward point opening 44 is prevented since the bottom or end of leg 52d of the resilient clip abuts the somewhat thicker side walls 30, 30' of body 12. Once this position is reached, the user releases finger-receiving element 52g and locking elements 521' spring" into lock-receiving notch 56b. With locking elements 521' in lock-receiving notch 56b, writing member 14 is maintained in place even as pressure is exerted on writing point 48, for example, during writing with the instrument.

After the user has finished writing, the procedure is reversed and writing member 14 is returned to its retracted position. Note that the cartridge channels 36, 38 are so arranged that writing member 16 cannot be moved into its extended writing position if writing instrument 14 is already in this position since the converging nature of the cartridge channels (at 37) provides room for only one of the writing members.

When it is required to put in a new writing member, for example, a refill or the like, clip 18 is removed, the old writing member is removed and a new one inserted (see for example. FIG.

Obviously, numerous modifications are possible in light of the above disclosure. It is to be understood, therefore, that the above-described embodiment is merely an example of the application of the principles of the present invention. Further embodiments will be apparent to those skilled in the art without departing from the spirit or scope of the invention as delineated by the scope of the following claims,

What is claimed is:

l. A writing instrument having a plurality of writing points comprising a body including body walls having opposed substantially flat faces and opposed side walls, each of said flat faces having a transverse dimension substantially greater than the transverse dimension of said side walls, said side walls extending between said flat faces to provide a substantial transverse rectangular configuration for said body, said flat faces and side walls forming channel walls and defining at least two elongated and straight channels, guide means extending inwardly from at least one of said flat faces and located between said channels, said channels being disposed in a substantially common plane intermediate said flat faces, said channels being disposed at an acute angle with respect to each other and converging into a common point opening at the bottom end thereof, the side walls of said body being tapered toward each other from substantially the top end to the bottom end thereof and converging at said point opening such that said body has a continuously decreasing cross section from substantially the top end to the bottom end thereof, at least two elongated writing members each having a longitudinal axis and each having a writing point at one end thereof, said writing members being respectively disposed in said separate channels in re tracted positions and mounted to be in contact with said guide means for substantially straight line reciprocation along their respective longitudinal axes within said separate channels from their respective retracted positions to extend their respective writing points through said point opening into an extended writing position, said writing members remaining at substantially constant angles with respect to each other during their entire straight line reciprocation in their respective channels, and respective manual actuating means operatively connected to each writing member and extending exteriorly of said body for manually moving said writing members in their respective channels at least toward said point opening and into said extended writing position, the spacing between the channel walls of said opposed substantially flat faces which define said channels being ofa dimension substantially equal to the dimensions of said writing members in transverse section, and the spacing between said opposed substantially flat faces being established to provide the requisite structural walls for said channels yet to minimize the dimension of said body at right angles to said plane whereby said body is relatively thin.

2. A writing instrument according to claim 1 wherein said two channels define two cartridge-receiving openings formed in the top end of said body, and clip means removably mounted on the top end of said body for substantially closing said cartridge-receiving openings after said writing members have been inserted i n their respective cartridge channels, said clip mu adapted to be removed from said body to enable said writing members to be inserted or withdrawn from their respective cartridge channels through said cartridge receiving openings.

3. A writing instrument according to claim 1 wherein said manual actuating means includes latch means for releasably maintaining said writing member in extended or retracted position.

4. The invention according to claim 1 wherein said opposed side walls are constructed and arranged to define track means for guiding said manual actuating means as said writing members are moved between said extended and retracted positions.

5. A writing instrument according to claim 4 wherein each of said manual actuating means comprises a U- shaped element having one leg connected to the top of said writing member and the other leg extending to be resiliently movable and including a finger-receiving element on its end thereof for sliding movement within element to be selectively received in one of said Sam track means' notches to determine said retracted and extended writ- 6. A writing instrument according to claim 5 wherein spaced notches are formed in said track means, and abutment means are formed on said finger-receiving 5 ing positions. 

1. A writing instrument having a plurality of writing points comprising a body including body walls having opposed substantially flat faces and opposed side walls, each of said flat faces having a transverse dimension substantially greater than the transverse dimension of said side walls, said side walls extending between said flat faces to provide a substantial transverse rectangular configuration for said body, said flat faces and side walls forming channel walls and defining at least two elongated and straight channels, guide means extending inwardly from at least one of said flat faces and located between said channels, said channels being disposed in a substantially common plane intermediate said flat faces, said channels being disposed at an acute angle with respect to each other and converging into a common point opening at the bottom end thereof, the side walls of said body being tapered toward each other from substantially the top end to the bottom end thereof and converging at said point opening such that said body has a continuously decreasing cross section from substantially the top end to the bottom end thereof, at least two elongated writing members each having a longitudinal axis and each having a writing point at one end thereof, said writing members being respectively disposed in said separate channels in retracted positions and mounted to be in contact with said guide means for substantially straight line reciprocation along their respective longitudinal axes within said separate channels from their respective retracted positions to extend their respective writing points through said point opening into an extended writing position, said writing members remaining at substantially constant angles with respect to each other during their entire straight line reciprocation in their respective channels, and respective manual actuating means operatively connected to each writing member and extending exteriorly of said body for manually moving said writing members in their respective channels at least toward said point opening And into said extended writing position, the spacing between the channel walls of said opposed substantially flat faces which define said channels being of a dimension substantially equal to the dimensions of said writing members in transverse section, and the spacing between said opposed substantially flat faces being established to provide the requisite structural walls for said channels yet to minimize the dimension of said body at right angles to said plane whereby said body is relatively thin.
 2. A writing instrument according to claim 1 wherein said two channels define two cartridge-receiving openings formed in the top end of said body, and clip means removably mounted on the top end of said body for substantially closing said cartridge-receiving openings after said writing members have been inserted into their respective cartridge channels, said clip means adapted to be removed from said body to enable said writing members to be inserted or withdrawn from their respective cartridge channels through said cartridge-receiving openings.
 3. A writing instrument according to claim 1 wherein said manual actuating means includes latch means for releasably maintaining said writing member in extended or retracted position.
 4. The invention according to claim 1 wherein said opposed side walls are constructed and arranged to define track means for guiding said manual actuating means as said writing members are moved between said extended and retracted positions.
 5. A writing instrument according to claim 4 wherein each of said manual actuating means comprises a U-shaped element having one leg connected to the top of said writing member and the other leg extending to be resiliently movable and including a finger-receiving element on its end thereof for sliding movement within said track means.
 6. A writing instrument according to claim 5 wherein spaced notches are formed in said track means, and abutment means are formed on said finger-receiving element to be selectively received in one of said notches to determine said retracted and extended writing positions. 